JPH10149020A - Image forming machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the toner fogging caused by the surface potential in both end parts of a photoreceptor drum being reduced under a prescribed value by arranging spacers formed of insulating material between the outside of image forming area of the photoreceptor drum and both end parts of a developing roller, respectively. SOLUTION: Spacers 60 formed of insulating material are arranged between both end parts of a photoreceptor drum and both end parts of a roller 532 constituting a developing roller, respectively. The spacers 60 are positioned on the outside about 1-2mm from the image area of the photoreceptor drum. Thus, when the roller 532 constituting the developing roller is pressed onto the photoreceptor drum, both end parts having the spacers 60 arranged thereon in the roller 532 are deformed, so that the range corresponding to the image area of the photoreceptor drum has a substantially uniform contact area. Therefore, the reduction in surface potential in both end parts of the image area in the photoreceptor drum by reducing the contact area in both the end parts is suppressed, and occurrence of toner fogging can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus equipped with an electrostatic latent image developing device for developing an electrostatic latent image formed on a photosensitive layer of a photosensitive drum, such as an electrostatic copying machine or a laser printer, into a toner image. The present invention relates to a process unit used for a forming machine and an image forming machine.

[0002]

2. Description of the Related Art In recent years, an image forming machine equipped with an electrostatic latent image developing device of a type in which an electrostatic latent image formed on a photosensitive layer of a photosensitive drum is developed into a toner image by a developer composed of a one-component toner has been developed. Widely used for practical use. This type of image forming machine is provided with a photosensitive drum rotatably disposed in order through a charging area, an electrostatic latent image forming area, a developing area, and a transfer area, and a photosensitive drum arranged in a charging area. A charging device for charging the surface to a specific polarity; a developing device disposed in the developing area to develop an electrostatic latent image formed on the peripheral surface of the photosensitive drum in the electrostatic latent image forming area into a toner image; and a transfer area. And a transfer means for transferring the toner image formed on the peripheral surface of the photosensitive drum to transfer paper. An electrostatic latent image developing device in which an electrostatic latent image is developed into a toner image by a developer composed of a one-component toner includes a developing housing having a developing chamber and a stirring chamber, and a developer holding apparatus provided in the developing chamber. A developing roller for holding the developer on the peripheral surface in the developing area and conveying the held developer to the developing area to apply it to the electrostatic latent image; Replenishing rollers as supply means for supplying the developer to the surface, stirring means disposed in the stirring chamber for stirring the developer supplied through the developer supply opening and sending the stirred developer to the development chamber;
A developer regulating unit that acts on a peripheral surface of the developing roller in a developer regulating region located between the developer retaining region and the developing region and regulates an amount of developer retained on the peripheral surface. ing. The developing roller includes a rotating shaft and a solid synthetic rubber roller fixed to the outer peripheral surface of the rotating shaft. The rubber roller is pressed against the peripheral surface of the photosensitive drum. The peripheral surface of the photosensitive drum is charged to 800 to 850 V, and a voltage of about 300 V is applied to the developing roller.

[0003]

Since the developing roller is pressed against the peripheral surface of the photosensitive drum, the electric charge charged on the photosensitive drum flows to the developing roller. There is no problem if the charge on the photoconductor drum flows uniformly to the developing roller side in the axial direction.However, when a portion that flows more than a predetermined amount occurs, the potential of the surface of the photoconductor drum at that location decreases, , So-called toner fog occurs. Since both ends of the developing roller are supported by bearings, the force of pressing against the photosensitive drum is applied from both ends via the bearings.
For this reason, due to the bending of the central portion of the developing roller, the pressure contact force at both ends of the developing roller becomes larger than at the central portion, and the contact area between the photosensitive drum and the developing roller increases at both ends. Accordingly, the amount of electric charge flowing to the developing roller from both ends of the photosensitive drum that are in pressure contact with both ends of the developing roller increases, so that the potential at both ends of the photosensitive drum becomes lower than the central part, and both ends of the photosensitive drum There is a problem that so-called toner fogging occurs in the portion.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and its main technical problem is to suppress a decrease in surface potential at both ends of a photosensitive drum and to keep the surface potential at both ends of the photosensitive drum at a predetermined level. It is an object of the present invention to provide an image forming apparatus and a process unit used for the image forming apparatus, which can prevent occurrence of so-called toner fogging caused by lowering the value.

[0005]

According to the present invention, in order to attain the above-mentioned main technical problems, the present invention is arranged rotatably and sequentially passes through a charging area, an electrostatic latent image forming area, a developing area and a transfer area. A photosensitive drum, a charger disposed in the charging area and charging the peripheral surface of the photosensitive drum to a specific polarity, a developing housing, and a developing housing mounted on the developing housing and pressed against the peripheral surface of the photosensitive drum. A developing device provided with a developing roller for holding a developer on a peripheral surface and transporting the held developer to a developing area to apply the electrostatic latent image to the developing device. There is provided an image forming machine, wherein spacers made of an insulating material are provided between an outer side of an image forming area of a drum and both ends of the developing roller.

Further, according to the present invention, a photosensitive drum rotatably disposed and sequentially passing through a charging area, an electrostatic latent image forming area, a developing area and a transfer area, and the photosensitive drum disposed in the charging area and A charger for charging the peripheral surface of the body drum to a specific polarity, a developing housing, and a developing device mounted on the developing housing and arranged in pressure contact with the peripheral surface of the photosensitive drum to hold a developer on the peripheral surface; A developing device provided with a developing roller for transferring the developer to the developing area and applying it to the electrostatic latent image, wherein an insulating layer is formed on a peripheral surface of the developing roller, An image forming machine is provided in which the insulating layer is formed thick at portions corresponding to both ends of the image forming area on the photosensitive drum.

Further, according to the present invention, a photosensitive drum rotatably disposed and sequentially passing through a charging area, an electrostatic latent image forming area, a developing area and a transfer area, and the photosensitive drum disposed in the charging area and A charger for charging the peripheral surface of the body drum to a specific polarity, a developing housing, and a developing device mounted on the developing housing and arranged in pressure contact with the peripheral surface of the photosensitive drum to hold a developer on the peripheral surface; A developing device provided with a developing roller for transferring the developer to the developing area and applying it to the electrostatic latent image, wherein the developing roller is provided at both ends of the image forming area on the photosensitive drum. An image forming apparatus is provided in which the outer diameter of a corresponding portion is configured to be small.

Further, according to the present invention, a photosensitive drum rotatably disposed and sequentially passing through a charging area, an electrostatic latent image forming area, a developing area and a transfer area, and the photosensitive drum disposed in the charging area and A charger for charging the peripheral surface of the body drum to a specific polarity, a developing housing, and a developing device mounted on the developing housing and arranged in pressure contact with the peripheral surface of the photosensitive drum to hold a developer on the peripheral surface; A developing unit having a developing roller for transporting the developer to a developing area and applying the developing agent to an electrostatic latent image; Wherein a spacer made of an insulating material is provided between both ends of the image forming apparatus.

Further, according to the present invention, a photosensitive drum rotatably disposed and sequentially passing through a charging area, an electrostatic latent image forming area, a developing area and a transfer area, and the photosensitive drum disposed in the charging area and A charger for charging the peripheral surface of the body drum to a specific polarity, a developing housing, and a developing device mounted on the developing housing and arranged in pressure contact with the peripheral surface of the photosensitive drum to hold a developer on the peripheral surface; And a developing unit having a developing roller for transporting the developer to the developing area and applying the same to the electrostatic latent image, in a process unit of an image forming machine, wherein an insulating layer is formed on a peripheral surface of the developing roller. And a process unit for the image forming machine, wherein the insulating layer is formed thick at portions corresponding to both ends of the image forming area on the photosensitive drum.

Further, according to the present invention, a photosensitive drum rotatably disposed and sequentially passing through a charging area, an electrostatic latent image forming area, a developing area and a transfer area, and the photosensitive drum disposed in the charging area and A charger for charging the peripheral surface of the body drum to a specific polarity, a developing housing, and a developing device mounted on the developing housing and arranged in pressure contact with the peripheral surface of the photosensitive drum to hold a developer on the peripheral surface; And a developing device having a developing roller for transporting the developer to the developing area and applying the developing agent to the electrostatic latent image, in a process unit of the image forming machine, wherein the developing roller is provided in the image forming area of the photosensitive drum. A process unit for an image forming apparatus, wherein the outer diameter of a portion corresponding to both ends is configured to be small. Other features of the present invention will become apparent from the following description.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of an image forming machine constituted according to the present invention and a process unit used in the image forming machine will be described in detail with reference to the accompanying drawings.
In the illustrated embodiment, a printer will be described as an example of an image forming apparatus configured according to the present invention.

FIG. 1 schematically shows an embodiment of a printer constructed according to the present invention. Printer 2
Is a small and low-speed laser printer used as a printing device such as a word processor in this embodiment, and includes a body housing 20 made of synthetic resin.
Is provided. The body housing 20 includes a box-shaped housing main body 21 whose upper part is open, and a cover 23 pivotally mounted on a shaft 22 provided on the upper part of the housing main body 21. The process unit 4 is detachably mounted at a substantially central portion of the body housing 20 configured as described above.

As shown in FIG. 2, the process unit 4 is composed of a photoreceptor unit 40 and an electrostatic latent image developing device supported by the photoreceptor unit 40 via a support shaft 5 so as to be swingable. Developing unit 50. The photoreceptor unit 40 includes a photoreceptor support means 41, and the photoreceptor support means 41 is provided with a pair of side wall members 411 spaced apart in the front-rear direction (only the rear side wall member is shown in FIG. 2). Shown) and the pair of side wall members 4
11 connecting members 412a, 412b connecting the lower portions
It has. The connecting members 412a and 412b are
The inner surfaces facing each other are arranged in parallel to form a charging means mounting space 412c in which a charging means described later is arranged between the two. The charging means mounting space 412c is located to face a charging area described later. The photoconductor supporting means 41 thus configured is integrally formed of a synthetic resin. At the upper end of the pair of side wall members 411 constituting the photoconductor supporting means 41 on the developing unit 50 side, mounting holes 4 are provided.
14 are provided. By inserting a support shaft 5 made of a metal bar disposed in a later-described developing housing of the developing unit 50 into a mounting hole 414 provided in the supporting portion 413, the photosensitive unit 40 and the developing unit 50 can be connected to each other. Is swingably supported.

The photosensitive unit 40 includes a photosensitive drum 42 having a photosensitive layer formed on a peripheral surface. The photosensitive drum 42 has a rotating shaft 421. The rotating shaft 421 is rotatably supported by a pair of side wall members 411 constituting the photosensitive member supporting means 41. That is, it is driven to rotate so as to sequentially pass through the charging area 422, the electrostatic latent image forming area 423, the developing area 424, and the transfer area 425. Charge area 422
The charging means 43 is disposed in the charging means mounting space 412c, which is located at a position opposite to the lower peripheral surface of the photosensitive drum 42. The charging means 43 includes a charging corona discharger 431 serving as a charger disposed in parallel with the photoreceptor drum 42 along the axial direction, and a charger holding member made of synthetic resin for mounting and holding the charging corona discharger. Member 43
The charging device holding member 432 is fitted in the charging means mounting space 412c and is positioned at a predetermined position. The charging unit 43 configured as described above charges the peripheral surface of the photosensitive drum 42 to 800 to 850V.
Further, between the charging area 422 and the transfer area 425, a foreign matter collecting brush 44 which is in contact with the peripheral surface of the photosensitive drum 42 is provided along the axial direction of the photosensitive drum 42. The paper dust collecting brush 44 is made of acrylic fiber or the like and has substantially the same length as the length of the photosensitive drum 42 in the axial direction. The paper dust collecting brush 44 is integrally formed with the charger holding member 432 and extends in the axial direction of the photosensitive drum 42. Brush support member 4 disposed along
40. The charging device holding member 43
The upper end of the projection 2 is formed between the charging corona discharger 431 disposed in the charging area 422 and the foreign matter collecting brush 44 so as to protrude so as to be close to the peripheral surface of the photosensitive drum 42. 47. The toner intrusion preventing wall 47 is attached to the peripheral surface of the photosensitive drum 42 and is removed by the foreign matter collecting brush 44 together with the foreign matter such as paper dust. In addition, it has a function of preventing intrusion on the charging corona discharger 431. As a result, the toner whose movement has been blocked by the toner intrusion prevention wall 47 is deposited on the horizontal piece near the toner intrusion prevention wall 47 of the brush support member 440.

The transfer paper fed from diagonally upper left in FIG. 2 is directed to a transfer area 425 on the peripheral surface of the photosensitive drum 42 between a pair of side wall members 411 constituting the photosensitive member support means 41. A lower guide plate 451 that constitutes one of the pre-transfer guide plate pair 45 that guides the lower guide plate 451 is provided, and the lower guide plate 451 is integrally formed with the pair of side wall members 411. A plurality of guide ribs 451a are integrally formed on the upper surface of the lower guide plate 451 at intervals in the longitudinal direction (the direction perpendicular to the paper surface in FIG. 2). The lower guide plate 451 is also provided with a plurality of reinforcing ribs 45 on the lower surface at intervals in the longitudinal direction (the direction perpendicular to the paper surface in FIG. 2).
1 b is integrally formed, and the reinforcing rib 451 b is configured to abut on the support shaft 5. Therefore,
Even if the lower guide plate 451 is pressed by the upper surface thereof and bends, the reinforcing ribs 451b abut on the support shaft 5 to prevent the lower guide plate 451 from bending. Also, the lower guide plate 451
Is a pair of side wall members 41 constituting the photoreceptor support means 41.
1 serves as a connecting member for connecting the upper portions to each other, and the rigidity of the photosensitive member supporting means 41 can be improved. Further, in the illustrated embodiment, since the lower guide plate 451 is integrally formed with the pair of side wall members 411, the positional relationship with respect to the photosensitive drum 42 rotatably supported by the pair of side wall members 411 can be determined with high precision. Can be maintained. Note that the lower guide plate 4 in the illustrated embodiment is used.
Numeral 51 functions as a member for preventing the photosensitive drum 42 from contacting the photosensitive layer when the process unit 4 is attached and detached, and also functions as a member for preventing the developing unit 50 from touching a later-described developing roller. It also has a function of preventing toner scattered from the surface of the roller from adhering to the transfer paper or the transfer path of the transfer paper.

A post-transfer guide plate 46 for guiding the transfer paper transferred in the transfer area 425 to a fixing means described later is disposed between the pair of side wall members 411 constituting the photosensitive member supporting means 41. The post-transfer guide plate 46 is formed integrally with the pair of side wall members 411. Therefore, the post-transfer guide plate 46 functions as a connecting member for connecting the pair of side wall members 411 constituting the photoconductor supporting unit 41 to each other, and can improve the rigidity of the photoconductor supporting unit 41. The post-transfer guide plate 4 in the illustrated embodiment.
6 can also function as a contact preventing member for the photosensitive layer of the photosensitive drum 42 when the process unit 4 is attached or detached.

Next, the developing unit 50 as an electrostatic latent image developing device will be described. The developing unit 50 in the illustrated embodiment includes a developing housing 51 in which a developer composed of one-component toner is stored. The developing housing 51 has a bottom wall 511 and a front wall and a rear wall 512 (FIG. 2) formed to stand upright from front and rear ends (ends in a direction perpendicular to the paper surface in FIG. 2) of the bottom wall 511.
Only the rear side wall) and a left side wall 513, which are integrally formed of a synthetic resin and define a stirring chamber 514 and a developing chamber 515. A stirring chamber 51 is provided on a bottom wall 511 of the developing housing 51.
A partition wall 516 provided in the front-rear direction (the direction perpendicular to the paper surface in FIG. 2) between the developing chamber 4 and the developing chamber 515 is integrally formed. Both left and right surfaces of the partition wall 516 are formed on arcuate guide surfaces 516a and 516b. Between the front and rear side walls 512 constituting the developing housing 51, a connecting member 517 provided at the upper part on the side of the developing chamber 515 is provided, and is formed integrally with the front and rear side walls 512. A toner supply hole 518 is formed in the rear side wall 512 of the developing housing 51.
8 is fitted with a cap 519. At the upper end of the developing housing 51 on the side of the developing chamber 515, the support shaft 5 is provided so as to penetrate the front and rear side walls 512. The photosensitive unit 4 is provided at both ends of the support shaft 5.
A pair of side wall members 41 constituting the photosensitive member supporting means 41
By fitting the mounting holes 414 provided in the first support portion 413, the photoconductor unit 40 and the developing unit 50 are supported so as to be able to swing mutually. The photoconductor unit 4
0 and the developing housing 51
A coil spring 52 serving as a spring means is interposed between the front end and the rear end of the photosensitive member supporting means 41 and the developing housing 5.
Numerals 1 are urged to draw each other with the support shaft 5 as a fulcrum. The developing housing 51 is open above and to the right, that is, on the photoconductor unit 40 side.

In the developing housing 51, a developing roller 53, a supply roller 54, a stirring means 55 and a developer regulating means 56 are provided. The developing roller 53 is
A rotating shaft 531 provided in the developing chamber 515 of the developing housing 51 and rotatably mounted on the front and rear side walls 512 constituting the developing housing 51, and a solid synthetic rubber roller fixed to the outer peripheral surface of the rotating shaft 531 532. The rotating shaft 531 can be formed from an appropriate metal material such as stainless steel. Solid synthetic rubber roller 53
2 is made of a relatively flexible and conductive material, for example, a conductive solid synthetic rubber such as urethane rubber. In the illustrated embodiment, a solid synthetic rubber roller 5 is used.
The surface roughness of the peripheral surface of No. 32, that is, the ten-point average roughness Rz specified in JIS B 0601 is set to 5.0 to 12.0. The volume resistance of the solid synthetic rubber roller 532 is set to about 10 ⁴ to 10 ⁹ Ω · cm. The roller hardness of the solid synthetic rubber roller 532 is set to 60 to 80 in Asker C hardness in the illustrated embodiment. The roller 532 of the developing roller 53 configured as described above is exposed through a right opening formed in the developing housing 51, and is exposed to the photosensitive drum 42.
Is positioned opposite to. The peripheral surface of the roller 532 constituting the developing roller 53 is pressed against the peripheral surface of the photosensitive drum 42 in the developing region, and the peripheral surface of the roller 532 is slightly elastically compressed at the pressed nip. ing. Rotating shaft 53 of developing roller 53
1 is driven to rotate from the lower side to the upper side in a direction indicated by an arrow by a driving unit (not shown), that is, in a developing area which is a contact portion between the roller 532 and the photosensitive drum 42. The rotation of the rotation shaft 531 causes the roller 532 to rotate.
The roller 532 is also driven to rotate in the direction indicated by the arrow, and the peripheral surface of the roller 532 is sequentially moved through the developer holding area 533, the developer regulating area 534, and the developing area 424. In the illustrated embodiment, a constant voltage of 300 V is applied to the rotating shaft 531 of the developing roller 53.

The replenishing roller 54 is disposed in the developing chamber 515 of the developing housing 51 in parallel with the developing roller 53, and is rotatably mounted on the front and rear side walls 512 constituting the developing housing 51. A shaft 541;
And a roller 542 fixed to the outer peripheral surface of the rotating shaft 541. The rotating shaft 541 can be formed of an appropriate metal material such as stainless steel, similarly to the rotating shaft 531 of the developing roller 53. The roller 542 is made of foam such as foamed silicone or foamed urethane. The roller 542 is a roller 5 of the developing roller 53 in a developer holding region 533 which is a nip portion with the developing roller 53
32. Roller 54 of supply roller 54
The hardness of the foam constituting the developing roller 2 is considerably smaller than the hardness of the roller 532 constituting the developing roller 53 (for example, about 35 in Asker C hardness), and the roller 542 is pressed against the roller 532 of the developing roller 53. It is desirable that the roller 542 be elastically compressed by about 0.1 to 0.6 mm in the nip area. Roller 5
42 also has conductivity, and its volume resistance is 10 ² to 1
It is set to about 0 ⁶ Ω · cm. The rotating shaft 541 of the replenishing roller 54 is rotated from the upper side to the lower side in a direction indicated by an arrow by a driving unit (not shown), that is, in a developer holding area 533 which is a nip portion between the roller 542 and the roller 532 of the developing roller 53. I'm sullen. Rotary axis 5
Due to the above rotation of the roller 41, the roller 542 is also driven to rotate in the direction shown by the arrow. In the illustrated embodiment,
The rotation shaft 541 of the supply roller 54 has the developing roller 53
A constant voltage of 450 V, which is higher than the applied voltage, is applied.

The peripheral speed V1 of the photosensitive drum 42, the peripheral speed V2 of the developing roller 53, and the peripheral speed V3 of the replenishing roller 54 are set in a relationship of V1 <V2 <V3.
In the illustrated embodiment, the relationship between the peripheral speed V1 of the photosensitive drum 42 and the peripheral speed V2 of the developing roller 53 is as follows.
1.2V1 ≦ V2 ≦ 2.5V1, the peripheral speed V2 of the developing roller 53 and the peripheral speed V3 of the replenishment roller 54 are set.
Is set to be 1.0V2 ≦ V3 ≦ 2.0V2. When the peripheral speed V2 of the developing roller 53 becomes 1.2 V1 or less, the supply of the developer to the photosensitive drum 42 becomes insufficient, and the image density is reduced. When the peripheral speed V2 of the developing roller 53 becomes 1.2 V1 or less, the scraping action of the developing roller 53 against the non-transferred developer attached to the photosensitive drum 42 after the transfer is reduced. This causes a so-called offset fog to occur because the photoreceptor drum 42 cannot be removed. On the other hand, when the peripheral speed V2 of the developing roller 53 becomes 2.5 V1 or more, the driving torque of the developing roller 53 increases, and the developer is scattered by centrifugal force. Further, when the peripheral speed V3 of the supply roller 54 becomes 1.0 V2 or less, the supply of the developer to the developing roller 53 becomes insufficient, which causes a decrease in image density. Also, the peripheral speed V of the supply roller 54
When 3 is 1.0 V2 or less, the action of scraping the peripheral surface of the developing roller 53 by the replenishing roller 54 is weak. Therefore, if the non-transferred developer adhered to the photosensitive drum 42 adheres to the developing roller 53 after the transfer, It becomes difficult to remove the adhered developer, and the adhered developer causes a so-called ghost phenomenon that appears during the next development. On the other hand, when the peripheral speed V3 of the supply roller 54 becomes 2.0 V2 or more, the supply roller 54
, The developer tends to stay above the nip portion between the supply roller 54 and the developing roller 53, which causes a shortage of the developer supply to the developing roller 53.

In the stirring chamber 514 of the developing housing 51, a stirring means 55 is provided. The stirring means 55
A rotating shaft 551 rotatably mounted on the front and rear side walls 512 constituting the developing housing 51, a stirring member 552 fixed to the rotating shaft 551, and An elastic stirring sheet member 553 attached to the stirring member 552 is included.
The stirring member 552 is formed of a synthetic resin,
A plurality of openings are provided in a longitudinal direction (a direction perpendicular to the paper surface in FIG. 2). The stirring sheet member 553 is made of, for example, polyethylene terephthalate (PET) having flexibility and elasticity.
P) It is formed of resin, and is fixed to the edge of the tip of the stirring member 552 by an adhesive or the like. The stirring means 55 thus configured is continuously driven to rotate in a direction indicated by an arrow in FIG. 2 by a driving means (not shown).

The developer regulating means 56 is a regulating blade 5 made of a thin flexible steel plate which is pressed against the peripheral surface of the roller 532 constituting the developing roller 32.
61 are provided. The regulating blade 561 is, for example,
It is made of a stainless steel plate or a spring steel plate having a thickness of about 0.1 to 0.2 mm, and has a longitudinal dimension substantially the same as the length of the roller 532 constituting the developing roller 53. The regulating blade 561 has a mounting portion 561a and a regulating portion 561b. A regulating member 562 made of urethane rubber is mounted on the surface (on the side facing the developing roller 32) of the regulating portion 561b constituting the regulating blade 561. In the illustrated embodiment, the restricting member 562 has a semicircular cross section with a radius of about 1 mm, has substantially the same length as the longitudinal dimension of the restricting blade 561, and has a flat surface on the surface of the restricting portion 561b. Mounted with adhesive. Mounting part 561 of regulating blade 561
a is a blade mounting portion 5 provided at an open end of the bottom wall 511 of the developing housing 51 on the photoconductor unit 40 side.
11a, it is clamped and attached by the holding plate 563. Mounting part 561a of regulating blade 561 and holding plate 5
63 and between the mounting portion 561a and the developing housing 51.
In the illustrated embodiment, elastic members 564 and 564 made of a sheet material of urethane rubber having a thickness of about 0.2 to 0.3 mm are arranged between the blade mounting portions 511a. The blade mounting portion 511a of the developing housing 51, the mounting portion 561a of the regulating blade 561, and the elastic member 56
4, 564 and the holding plate 563 are provided with a plurality of screw insertion holes at predetermined positions at positions corresponding to each other in the longitudinal direction. A plurality of screws 565 are inserted into a plurality of screw insertion holes provided in each of the above members from the blade mounting portion 511a side of the developing housing 51, and a screw portion 565a formed at the tip of the screw 565 is pressed. By screwing into a female screw 563a formed in a screw insertion hole provided in the plate 563, the mounting portion 561a of the regulating blade 561 is pressed onto the blade mounting portion 511a of the developing housing 51 via elastic members 564 and 564. 563 and clamped and fixed. As described above, the mounting portion 561a of the regulating blade 561 is
Since the screw 565 is attached to the blade attachment portion 511a of the developing housing 51 via the intermediate members 64, 564, the tightening force of the screw 565 is dispersed by the elastic members 564, 564. Accordingly, deformation of the holding plate 563 can be suppressed even if its rigidity is not very high, and deformation of the regulating blade 561 due to deformation of the holding plate 563 by the tightening force of the screw 565 can be reduced. In the illustrated embodiment, an example is shown in which the elastic members 564 and 564 are disposed on both sides of the mounting portion 561a of the regulating blade 561, but only between the mounting portion 561a of the regulating blade 561 and the pressing plate 563. Even when the elastic member 564 is provided, the dispersion of the tightening force is slightly reduced as compared with the case where the elastic members are provided on both sides, but it is possible to obtain a sufficient operation and effect of alleviating the deformation of the regulating blade 561.

A fulcrum member mounting portion 511b is provided above the blade mounting portion 511a in the developing housing 51.
Are formed in the front-rear direction (the direction perpendicular to the plane of FIG. 2). The fulcrum member mounting portion 511b is formed by an arc-shaped groove in the illustrated embodiment. A fulcrum member 566 is provided at the fulcrum member attachment portion 511b. The fulcrum member mounting portion 511b is made of, for example, a 2 mm metal round bar in the illustrated embodiment, and has substantially the same length as the longitudinal dimension of the regulating blade 561. The fulcrum member 566 is placed on the fulcrum member attachment portion 511b, and the back surface between the mounting portion 561a and the restriction portion 561b of the restriction blade 561 (the surface opposite to the surface on which the restriction member 562 is mounted).
It is configured to abut against. The fulcrum member 56
6 is desirably disposed at such a position that the contact position of the regulating blade 561 is as far as possible from the regulating member 562 in order to achieve downsizing of the regulating blade 561. The developer regulating means 56 thus configured is such that the regulating blade 561 is flexed with the fulcrum member 566 as a fulcrum, and the regulating member 562 mounted on the surface of the regulating portion 561b moves the developing roller 53 in the developer regulating area 534. Constituting roller 5
32 is pressed against the peripheral surface. Developer regulating means 56
Is configured as described above, and since the fulcrum member 566 serving as the fulcrum of the deflection of the regulating blade 561 is made of a round bar, a relatively accurate fulcrum can be obtained at low cost. In the illustrated embodiment, the fulcrum member 5
Although an example in which a round bar is used as 66 is shown, a square bar may be used.

The developing housing 51 is provided with a lid 57 for covering the opened upper part. The lid 57 is made of a synthetic resin, and is fixed to an upper surface of the front and rear side walls 512, the left side wall 513, and the upper surface of the connecting member 517 constituting the developing housing 51 by an adhesive. A regulating portion 571 that extends in the front-rear direction (a direction perpendicular to the paper surface in FIG. 2) and protrudes toward the developing chamber 515 is integrally formed on the inner surface of the lid 57 at a position facing the supply roller 54. A predetermined interval is provided between the lower end of the regulating portion 571 and the outer peripheral surface of the roller 542 constituting the supply roller 54. In the illustrated embodiment, a sheet-shaped seal member 58 is attached to the connecting member 517 constituting the developing housing 51. The sheet-shaped sealing member 58 is made of, for example, polyethylene terephthalate (P
It is made of a sheet member having flexibility and elasticity, such as ETP) resin, and has substantially the same length as the axial length of the roller 532 constituting the developing roller 53. One end of the sheet-shaped sealing member 58 is connected to the connecting member 517.
Is fixed to the developing roller 53 by a fixing means such as an adhesive.
2 is elastically brought into contact with the peripheral surface. The sheet-shaped sealing member 58 thus configured is provided together with the blade 561 of the developer regulating means 56 on the developing housing 5.
The developer is prevented from scattering from the opening on the side of the photoconductor unit 40.

In the process unit 4 configured as described above, the roller 532 constituting the developing roller 53 pressed against the peripheral surface of the photosensitive drum 42 is slightly elastically compressed at the pressure contact portion. Since 53 has both ends supported by bearings, the force of pressing against the photosensitive drum 42 is applied from both ends via the bearings. For this reason, due to the bending of the central portion of the roller 532 constituting the developing roller, both ends of the roller 532 constituting the developing roller 53 have a greater pressure contact force than the central portion, and the contact between the photosensitive drum 42 and the roller 532 is increased. The contact area increases at both ends. Therefore, the roller 5 on the photosensitive drum 42
The developing roller 53 is pressed from both ends in pressure contact with both ends of the developing roller 53.
Of the photosensitive drum 42, the potential at both ends of the photosensitive drum 42 becomes lower than that at the center, and the photosensitive drum 4
2 causes so-called toner fogging at both ends. Such a roller 5 constituting the developing roller 53
In order to prevent a decrease in the surface potential at both ends of the photosensitive drum due to the pressure contact with the photosensitive drum at 32, the following measures are taken in the present invention.

First, with reference to FIGS. 3 to 5, a description will be given of an embodiment of a measure for preventing a surface potential from decreasing at both ends of the photosensitive drum. In this embodiment, both ends of the photosensitive drum 42 and the rollers 53
2 and spacers 60 made of an insulating material between both end portions
Is an example in which each is disposed. The spacer 60 is made of a sheet material formed of, for example, polyethylene terephthalate (PETP) resin and having a thickness of about 0.3 to 0.4 mm, and a Teflon (trade name) having a small friction coefficient and excellent sliding characteristics on its surface. Etc. are applied. Further, the spacer 60 may be formed using a polyacetal resin or the like containing a wax having a small friction coefficient and good sliding characteristics. The spacer 60 includes a contact portion 601, an engaging portion 602 provided at one end of the contact portion 601, and a sticking portion 603 provided at the other end of the contact portion 601.
The contact portion 601 is formed to have a width of about 3 mm.
2 is formed to protrude laterally from the contact portion 601,
The sticking section 603 has a double-sided adhesive tape 604 mounted thereon. In the spacer 60 thus configured, the contact portions 601 are positioned at both ends of the roller 532 constituting the developing roller 53, and the engaging portion 602 is attached to the lower end of the regulating blade attachment portion 561 a in the developing housing 51 and to this. It is inserted and locked in a locking space formed between the pressing plate 563 and the pressing plate 563. Then, the double-sided adhesive tape 604 attached to the attaching portion 603 of the spacer 60 is attached to the attaching portions 510 formed on the front side wall and the rear side wall of the developing housing 51, respectively. As described above, the spacers 60, 60 provided between both ends of the photosensitive drum 42 and both ends of the roller 532 constituting the developing roller 53 are about 1 to 2 mm from the image area 420 of the photosensitive drum 42. Located outside. Therefore, when the roller 532 constituting the developing roller 53 is pressed against the photosensitive drum 42, both ends of the roller 532 where the spacers 60, 60 are disposed are deformed as shown in FIG. The area corresponding to the image area 420 has a substantially uniform contact area. Therefore, the photosensitive drum 42 and the roller 532 constituting the developing roller 53
A decrease in the surface potential at both ends of the image area 420 on the photosensitive drum 42 due to an increase in the contact area between the two ends of the image area 420 on the photosensitive drum 42 is suppressed.
It is possible to prevent so-called toner fogging caused by the surface potential at both ends of 0 being lower than a predetermined value.

Next, another embodiment of the spacer disposed between both ends of the photosensitive drum 42 and both ends of the roller 532 constituting the developing roller 53 will be described with reference to FIG. In this embodiment, spacers 62 composed of a cylindrical member formed of an insulating material are fitted and mounted on both ends of a roller 532 constituting the developing roller 53, respectively. The spacer 62 made of a cylindrical member is made of a synthetic resin having a small friction coefficient and good sliding characteristics.
The cylindrical portion 621 includes a cylindrical portion 621 and an annular stopper portion 622 integrally formed at one end of the cylindrical portion 621.
Has a thickness of about 0.3 to 0.4 mm. The spacers 62, 62 configured as described above are fitted to both ends of the roller 532 constituting the developing roller 53 as shown in the figure. The axial dimension of the cylindrical portion 621 constituting the spacer 62 is about 1 to 2 mm from the position corresponding to the image area 420 of the photosensitive drum 42 when the inner end thereof is mounted on the end of the roller 532. It is set to the length positioned outside. Therefore, when the roller 532 constituting the developing roller 53 is pressed against the photosensitive drum 42, the pressed portion performs the same operation as the embodiment shown in FIGS. 3 to 5 described above.

FIG. 7 shows still another embodiment of the spacer provided between both ends of the photosensitive drum 42 and both ends of the roller 532 constituting the developing roller 53. In this embodiment, a spacer 64 composed of a cylindrical member formed of an insulating material at both ends of the photosensitive drum 42 is provided.
64 are fitted and mounted. The spacer 64 made of a cylindrical member is made of a synthetic resin having a small friction coefficient and good sliding characteristics.
1 has an annular stopper portion 642 integrally formed at one end thereof, and the thickness of the cylindrical portion 641 is 0.3 to 0.4 m.
m. The spacers 64, 64 configured as described above are fitted to both ends of the photosensitive drum 42 as illustrated. In addition, the cylindrical portion 6 constituting the spacer 64
The inner end of 41 is positioned about 1 to 2 mm outside the position of the image area 420. Therefore, when the roller 532 constituting the developing roller 53 is pressed against the photosensitive drum 42, the pressed portion performs the same operation as in the embodiments shown in FIGS. 3 to 5 and 6 described above.

Next, another embodiment for preventing the surface potential from being lowered at both ends of the photosensitive drum will be described with reference to FIG. In this embodiment, an insulating layer 533 is formed of an insulating material having excellent sliding characteristics on a peripheral surface of a roller 532 constituting the developing roller 53.
33 are made thick portions 533a at both ends. The insulating layer 533 can be formed by immersing the roller 532 in a fluorine-based synthetic resin solution having a small coefficient of friction and good sliding characteristics, for example, and then drying the roller 532, and has a thickness of about 1 μm. Then, the synthetic resin solution is applied several times only to the thick portions 533a, which are both end portions, and dried, and the thickness is reduced to 2 to 3 μm.
m. Note that the thick portion 533a of the insulating layer 533 formed on the peripheral surface of the roller 532 constituting the developing roller 53 corresponds to the image area 420 of the photosensitive drum 42.
Are formed over portions corresponding to both ends of the. By configuring the peripheral surface of the roller 532 constituting the developing roller 53 as described above, the contact area of both ends of the roller 532 constituting the developing roller 53 in a state of being pressed against the photosensitive drum 42 is increased. Also, since the thick portions 533a of the insulating layer 533 corresponding to both ends of the image area 420 have high insulating properties, it is possible to suppress the flow of the charges charged on the surface of the photosensitive drum 42 to the developing roller side. Therefore, a decrease in the surface potential at both ends of the image area 420 on the photosensitive drum 42 due to an increase in the contact area at both ends is suppressed, and the image area 420 on the photosensitive drum 42 is suppressed.
, So-called toner fog, which is caused by the surface potential at both ends of the image forming device falling below a predetermined value, can be prevented.

FIG. 9 shows still another embodiment of a countermeasure for preventing the surface potential from decreasing at both ends of the photosensitive drum. In this embodiment, the outer diameter of both ends of the roller 532 constituting the developing roller 53 is smaller than the center by about 0.1 mm, and forms a small diameter portion 532a. The small-diameter portion 532a is formed in the image area 420 on the photosensitive drum 42.
Are formed over portions corresponding to both ends of the. Therefore, when the roller 532 constituting the developing roller 53 is pressed against the photosensitive drum 42, the photosensitive drum 4
The area corresponding to the second image area 420 has a substantially uniform contact area, and substantially the same operation and effect as those of the embodiment shown in FIGS. 3 to 5 can be obtained. The outer diameter of both ends of the roller 532 constituting the developing roller 53 is made smaller than that of the central part. You may comprise a drum shape.

The process unit 4 configured as described above is detachably mounted on the body housing 20 of the printer 2 as shown in FIG. That is, the upper part of the housing main body 21 constituting the body housing 20 is opened by turning the cover 23 constituting the body housing 20 of the printer 2 around the axis 22 counterclockwise in FIG. Next, the process unit 4 is mounted in the housing body 21 from above. The housing body 21
Inside, a positioning means (not shown) capable of mounting the photoconductor unit 40 of the process unit 4 at a predetermined position is provided. The process unit 4 is connected to the body housing 20.
When the cover 22 is attached to the housing body 21 of the
By turning clockwise in FIG. 1 around two directions, the upper part is closed.

As shown in FIG. 1, a lower part of a housing body 21 constituting a body housing 20 of the printer 2 includes
A laser unit 24 is provided. The laser unit 24 irradiates the photosensitive layer of the photosensitive drum 42 with a laser beam corresponding to print data from, for example, a word processor connected to the printer 2 in the electrostatic latent image forming area 423 of the process unit 4, Form a latent image. A fixing roller pair 25 is disposed on the downstream side of the post-transfer guide plate 46 on the housing body 21 constituting the body housing 20 of the printer 2, and a discharge roller pair 26 is disposed on the downstream side of the fixing roller pair 25. Are arranged. Further, a discharge tray 27 is provided downstream of the discharge roller pair 26.

In the cover 23 constituting the body housing 20 of the printer 2, a paper feed tray 28 on which transfer paper is placed is disposed at the upper left side in FIG. A paper feed roller 29 is provided downstream of the paper feed tray 28,
The paper feed roller 29 is driven to rotate in a direction indicated by an arrow in FIG. A friction pad 30 for separating sheets is provided opposite to the sheet feeding roller 29. Further, a non-contact type transfer roller 31 is provided in the transfer area 422 so as to face the photosensitive drum 42. The transfer roller 31 is formed of conductive urethane foam, and is rotatably supported by the cover 23. The transfer roller 31 is provided with collars (not shown) made of an insulating material such as a synthetic resin having an outer diameter larger than that of the transfer roller 31 at both ends thereof, and the collars are arranged in contact with the peripheral surface of the photosensitive drum 42. Has been
Accordingly, the transfer roller 31 is driven to slide while the photosensitive drum 42 rotates. The gap between the peripheral surface of the transfer roller 31 and the peripheral surface of the photosensitive drum 42 is 0.5 m.
m. A constant current of, for example, 10 μA is applied to the transfer roller 31 configured as described above.
An upper guide plate 452 constituting the other of the pre-transfer guide plate pair 45 is disposed on the cover 23.

The printer in the illustrated embodiment is configured as described above, and its operation will be described below. Each of the above members starts to operate based on a print command from a word processor (not shown) or the like, and the charging corona discharger 4
3, the surface photosensitive layer of the photosensitive drum 42 is substantially uniformly charged to a specific polarity. Next, a laser beam corresponding to print data from a word processor or the like is emitted from the laser unit 24 to the charged surface of the photosensitive layer of the photosensitive drum 42, and an electrostatic latent image is formed. The electrostatic latent image thus formed on the photosensitive layer of the photosensitive drum 42 is developed into a toner image by the developing operation of the developing unit 50. The developing operation of the developing unit 50 is described below.
Details will be described later. On the other hand, the transfer paper placed on the paper feed tray 28 is fed one by one by the action of the paper feed roller 29 and the friction pad 30. Then, the transfer paper is guided by the pre-transfer guide plate pair 45 and the photosensitive drum 42 and the transfer roller 3.
1 and the toner image formed on the photosensitive drum 42 is transferred onto the surface thereof. The transfer paper on which the toner image has been transferred is guided by the guide plate 46 after the transfer, and is conveyed to the fixing roller pair 25. The transfer paper on which the toner image has been heated and fixed by the fixing roller pair 25 is discharged onto a discharge tray 27 by the discharge roller pair 26. On the other hand, when the peripheral surface of the photosensitive drum 42 that has passed through the transfer area 425 passes through the foreign matter collecting brush 44, foreign matter such as paper dust adhered to the peripheral surface is removed by the foreign matter collecting brush 44. At this time, residual toner adhering to the peripheral surface of the photosensitive drum 42 is removed together with foreign matter such as paper dust. The removed residual toner may fall without being reliably captured by the foreign matter collecting brush 44. If the dropped toner accumulates on the charging corona discharger 431, it causes charging unevenness. In the illustrated embodiment, the toner intrusion prevention wall 47 causes the dropped toner to move toward the charging corona discharger 431. Intrusion is prevented.

Next, the developing operation of the developing unit 50 will be described. By starting the operation of the developing unit 50,
The developing roller 53, the supply roller 54, and the stirring means 5
5 are rotationally driven in directions indicated by arrows by drive means (not shown). Stirring member 55 constituting stirring means 55
2 and the stirring sheet member 553 rotate in the direction indicated by the arrow, the developer accommodated in the stirring chamber 514 passes over the partition wall 516 while being stirred, and
Is supplied into the developing chamber 514 from above. At this time, the regulating portion 571 formed on the inner surface of the lid 57 causes
The amount of the developer supplied into the developing chamber 514 is limited so as not to be excessive. The developer supplied by the agitating unit 55 in this manner rides on the roller 542 of the supply roller 54 and is transported to the nip portion which is the developer holding area 533 with the roller 532 of the developing roller 53. Since the supply roller 54 and the developing roller 53 rotate in the same direction from the upper side to the lower side in the developer holding area 533 which is a nip portion as described above, the supply roller 54 and the developing roller 53
The developer is sufficiently supplied to the developer, and the shortage of the developer can be prevented. The replenishing roller 54 and the developing roller 5
3 is a developer holding area 533 which is a nip portion as described above.
, The motor can be driven reliably without requiring a large driving force.

As described above, the developer conveyed to the developer holding area 533, which is a nip portion between the supply roller 54 and the developing roller 53, is supplied to the roller 53 constituting the developing roller 53.
2 and is conveyed toward the developer regulating area 534. At this time, the supply roller 54 and the developing roller 53
Are rotated in the same direction from the upper side to the lower side in the developer holding area 533 which is the nip portion as described above, so that the developer is held by the developing roller 53 through both nip portions, and the developer is regulated. Since they are conveyed to the 534 and the developing zone 535, they are rubbed against each other when passing through the nip portion and are sufficiently charged, so that the occurrence of so-called fog is prevented.

In the developer regulating area 534, a regulating member 562 mounted on the surface of the blade 561 constituting the developer regulating means 56 acts on the developer held on the peripheral surface of the roller 532 of the developing roller 53. And the roller 532
The developer held on the peripheral surface is regulated to a required amount to form a thin layer. In the developer regulation area 534, the bottom wall 51 of the development housing 51 is regulated by the regulation member 562 attached to the blade 561 of the developer regulation means 56.
The developer scraped off onto 1 is conveyed along the guide surface 516b of the partition wall 516 without stopping because the supply roller 54 is rotated in the direction shown by the arrow.

As described above, the regulating member held on the peripheral surface of the roller 532 constituting the developing roller 53 in the developer retaining area 533 and the regulating member mounted on the regulating blade 561 of the developer regulating means 56 in the developer regulating area 534. 562
The developer formed in a thin layer by the action of is transported to the developing area 424 with rotation in the direction of the arrow. In the developing area 424, a developer is applied to the electrostatic latent image on the electrostatic photosensitive member disposed on the peripheral surface of the photosensitive drum 42,
The electrostatic latent image is developed into a toner image. For example, the electrostatic latent image has a non-image area charged to about +600 V and + 12V.
It has an image area charged to about 0 V, and toner as a developer is attached to the image area (so-called reversal development). The photosensitive drum 42 and the developing roller 53 are driven to rotate in a direction indicated by an arrow in FIG.
In the developing area 535, the peripheral surface of the photosensitive drum 42 and the peripheral surface of the roller 532 constituting the developing roller 53 are both moved upward from below in the same direction. Roller 532
And the peripheral speed V1 of the photosensitive drum 42 are as follows.
Since 2V1 ≦ V2 ≦ 2.5V1, a sufficient amount of developer is conveyed to the developing area 535 by the roller 532 of the developing roller 53, and the peripheral surface of the roller 532 slides on the peripheral surface of the photosensitive drum 42. The developer that has once adhered to the non-image portion of the electrostatic latent image is appropriately peeled off by the rubbing action, so that a good toner image having an appropriate development density and no fog can be obtained. On the other hand, the used developer held on the peripheral surface of the roller 532 constituting the developing roller 53 and passing through the developing area 424 is transferred to the surface of the replenishing roller 54 at the nip portion between the developing roller 53 and the replenishing roller 54. It is. Since the peripheral speed of the supply roller 54 is set to be higher than the peripheral speed of the developing roller 53, the developer is moved in the nip portion. The adhesive force of the transfer developer can be weakened and collected, so that a so-called ghost caused by the non-transfer developer adhered to the developing roller 53 can be prevented.

Although the present invention has been described based on an embodiment in which the present invention is applied to a printer, the present invention is not limited to the illustrated embodiment, and can be applied to, for example, an electrostatic copying machine. Various changes or modifications can be made without departing from the scope of the technical idea of the present invention.

[0040]

Since the image forming apparatus and the process unit used in the image forming apparatus according to the present invention are constructed as described above, the following operational effects can be obtained.

That is, according to the present invention, since the spacer made of an insulating material is disposed between the outside of the image forming area of the photosensitive drum and both ends of the developing roller, the developing roller is pressed against the photosensitive drum. In this state, the area corresponding to the image area of the photosensitive drum has a substantially uniform contact area.
For this reason, a decrease in the surface potential at both ends of the image area on the photosensitive drum due to an increase in the contact area between both ends of the photosensitive drum and the developing roller is suppressed, and the surface of both ends of the image area on the photosensitive drum is suppressed. It is possible to prevent so-called toner fogging caused by the potential dropping below a predetermined value.

According to the present invention, an insulating layer is formed on the peripheral surface of the developing roller, and the insulating layer is formed thick at portions corresponding to both ends of the image forming area on the photosensitive drum. Therefore, even if the contact area at both ends of the developing roller is increased while the developing roller is pressed against the photosensitive drum, both ends are highly insulative, so that the charge charged on the surface of the photosensitive drum is transferred to the developing roller. The flow can be suppressed.
Therefore, a decrease in the surface potential at both ends of the photosensitive drum due to an increase in the contact area at both ends is suppressed, and so-called toner fogging caused by a surface potential at both ends of the photosensitive drum falling below a predetermined value is prevented. can do.

Further, according to the present invention, since the developing roller has a small outer diameter at a portion corresponding to both ends of the image forming area on the photosensitive drum, the developing roller is pressed against the photosensitive drum. In this state, an increase in the contact area at both ends can be suppressed. Therefore, a decrease in the surface potential at both ends of the photosensitive drum due to an increase in the contact area at both ends is suppressed, and so-called toner fogging caused by a surface potential at both ends of the photosensitive drum falling below a predetermined value is prevented. can do.

[Brief description of the drawings]

FIG. 1 is a front view schematically showing an embodiment of an image forming apparatus configured according to the present invention.

FIG. 2 is a cross-sectional view of the image forming apparatus configured according to the present invention shown in FIG.

FIG. 3 is a cross-sectional view of a main part showing one embodiment of a measure for preventing a decrease in surface potential at both ends of a photosensitive drum applied to the image forming machine shown in FIG. 2;

FIG. 4 is a plan view of a spacer used to prevent a decrease in surface potential at both ends of the photosensitive drum in FIG. 3;

FIG. 5 is an explanatory diagram showing a state in which the photosensitive drum and the developing roller are pressed against each other in a measure for preventing a decrease in surface potential at both ends of the photosensitive drum in FIG. 3;

FIG. 6 shows another embodiment of the spacer used for preventing the surface potential from being lowered at both ends of the photosensitive drum.
FIG. 4 is a longitudinal sectional view in which a spacer is mounted on a developing roller.

FIG. 7 shows another embodiment of a spacer used to prevent a decrease in surface potential at both ends of the photosensitive drum.
FIG. 4 is a longitudinal sectional view in which a spacer is mounted on a photosensitive drum.

FIG. 8 is a cross-sectional view of a principal part showing another embodiment of a measure for preventing a decrease in surface potential at both ends of a photosensitive drum applied to the image forming machine shown in FIG. 2;

FIG. 9 is a cross-sectional view of a main part showing still another embodiment of a measure for preventing a decrease in surface potential at both ends of a photosensitive drum applied to the image forming machine shown in FIG. 2;

[Explanation of symbols]

 2: printer 4: process unit 5: support shaft 20: body housing 21: housing body 23: cover 24: laser unit 25: fixing roller pair 26: discharge roller pair 27: discharge tray 28: paper feed tray 29: paper feed Roller 30: Friction pad 31: Transfer roller 40: Photoconductor unit 41: Photoconductor support means 42: Photoconductor drum 43: Charging means 44: Foreign matter collecting brush 45: Guide plate pair before transfer 46: Guide plate after transfer 47: Toner Intrusion prevention wall 50: developing unit 51: developing housing 52: coil spring 53: developing roller 54: supply roller 55: stirring means 56: developer regulating means 57: lid 58: sheet-shaped seal member 60, 62, 64: spacer 431 : Charging corona discharger 411: side wall member of photoconductor support means 412: series of photoconductor support means Coupling member 422: Charging area 423: Electrostatic latent image formation area 424: Development area 425: Transfer area 470: Toner intrusion prevention wall 514: Stirring chamber 515: Development chamber 517: Connection member of development housing 533: Developer holding area 534 : Developer regulating area 561: regulating blade 561 a: regulating blade mounting portion 561 b: regulating blade regulating portion 562: regulating member 566: fulcrum member

Continued on the front page (72) Inventor Shizushi Kado 1-2-28 Tamazo, Chuo-ku, Osaka-shi Mita Kogyo Co., Ltd. (72) Inventor Atsushi Fujii 1-2-28 Tamazo, Chuo-ku, Osaka-shi Mita (72) Inventor Hideki Taniguchi 1-2-28 Tamazo, Chuo-ku, Osaka-shi Mita Corporation (72) Inventor Masaru Goto 1-2-28 Tamazo, Chuo-ku, Osaka Mita Corporation In company

Claims (12)

[Claims] 1. A photosensitive drum rotatably disposed to sequentially pass through a charging area, an electrostatic latent image forming area, a developing area, and a transfer area, and a peripheral surface of the photosensitive drum disposed in the charging area. A charging device charged to a specific polarity; a developing housing; and a developer housing, which is mounted on the developing housing and is disposed in pressure contact with the peripheral surface of the photosensitive drum, holds the developer on the peripheral surface, and conveys the retained developer to a developing area. A developing device having a developing roller for applying the latent image to the electrostatic latent image, wherein an insulating material is provided between an outer side of the image forming area of the photosensitive drum and both ends of the developing roller. An image forming machine, wherein spacers comprising: 2. The image forming apparatus according to claim 1, wherein said spacer is made of a sheet material formed of a synthetic resin, and both ends thereof are attached to said developing housing. 3. The image forming apparatus according to claim 1, wherein the spacer is formed of a cylindrical member formed of a synthetic resin, and is fitted at both ends of the developing roller. 4. The image forming apparatus according to claim 1, wherein said spacer is formed of a cylindrical member formed of a synthetic resin, and is fitted to both ends of said photosensitive drum. 5. A photosensitive drum rotatably disposed to sequentially pass through a charging area, an electrostatic latent image forming area, a developing area and a transfer area, and a peripheral surface of the photosensitive drum disposed in the charging area. A charging device charged to a specific polarity; a developing housing; and a developer housing, which is mounted on the developing housing and is disposed in pressure contact with the peripheral surface of the photosensitive drum, holds the developer on the peripheral surface, and conveys the retained developer to a developing area. And a developing device having a developing roller for applying the latent image to the electrostatic latent image, wherein an insulating layer is formed on a peripheral surface of the developing roller, and the insulating layer is An image forming machine, wherein portions corresponding to both ends of an image forming area of a drum are formed thick. 6. A photosensitive drum rotatably disposed to sequentially pass through a charging area, an electrostatic latent image forming area, a developing area, and a transfer area, and a peripheral surface of the photosensitive drum disposed in the charging area. A charging device charged to a specific polarity; a developing housing; and a developer housing, which is mounted on the developing housing and is disposed in pressure contact with the peripheral surface of the photosensitive drum, holds the developer on the peripheral surface, and conveys the retained developer to a developing area. A developing device provided with a developing roller for applying the electrostatic latent image to the electrostatic latent image, wherein the developing roller has an outer diameter of a portion corresponding to both ends of an image forming area on the photosensitive drum. An image forming machine characterized by having a small diameter. 7. A photosensitive drum rotatably disposed to sequentially pass through a charging area, an electrostatic latent image forming area, a developing area and a transfer area, and a peripheral surface of the photosensitive drum disposed in the charging area. A charging device charged to a specific polarity; a developing housing; and a developer housing, which is mounted on the developing housing and is disposed in pressure contact with the peripheral surface of the photosensitive drum, holds the developer on the peripheral surface, and conveys the retained developer to a developing area. A developing device having a developing roller for applying the latent image to the electrostatic latent image, and a process unit of the image forming machine, wherein a portion between an outer side of the image forming area on the photosensitive drum and both ends of the developing roller is provided. And a spacer made of an insulating material. 8. The process unit of an image forming machine according to claim 7, wherein said spacer is made of a sheet material formed of a synthetic resin, and both ends thereof are attached to said developing housing. 9. The process unit of an image forming machine according to claim 7, wherein said spacer is formed of a cylindrical member formed of a synthetic resin, and is fitted to both ends of said developing roller. 10. The process unit of an image forming machine according to claim 7, wherein said spacer is formed of a cylindrical member formed of a synthetic resin, and is fitted to both ends of said photosensitive drum. 11. A photosensitive drum rotatably disposed to sequentially pass through a charging area, an electrostatic latent image forming area, a developing area and a transfer area, and a peripheral surface of the photosensitive drum disposed in the charging area. A charging device charged to a specific polarity; a developing housing; and a developer housing, which is mounted on the developing housing and is disposed in pressure contact with the peripheral surface of the photosensitive drum, holds the developer on the peripheral surface, and conveys the retained developer to a developing area. A developing unit having a developing roller for applying the electrostatic latent image to the developing unit, wherein an insulating layer is formed on a peripheral surface of the developing roller, and the insulating layer is A process unit for an image forming machine, wherein portions corresponding to both ends of an image forming area of the photosensitive drum are formed thick. 12. A photosensitive drum rotatably disposed to sequentially pass through a charging area, an electrostatic latent image forming area, a developing area and a transfer area, and a peripheral surface of the photosensitive drum disposed in the charging area. A charging device charged to a specific polarity; a developing housing; and a developer housing, which is mounted on the developing housing and is disposed in pressure contact with the peripheral surface of the photosensitive drum, holds the developer on the peripheral surface, and conveys the retained developer to a developing area. A developing device having a developing roller for applying the electrostatic latent image to the developing unit, wherein the developing roller has a portion corresponding to both ends of an image forming area on the photosensitive drum. The process unit of the image forming machine, wherein an outer diameter of the process unit is configured to be small.